drm/probe-helper: Check epoch counter in output_poll_execute()

drm_helper_hpd_irq_event() checks the epoch counter to determine
connector status change. This was introduced in
commit 5186421c ("drm: Introduce epoch counter to drm_connector").
Do the same for output_poll_execute() so it can detect other changes
beside connection status value changes.

v2:
- Add Fixes tag (Daniel)

Fixes: 5186421c ("drm: Introduce epoch counter to drm_connector")
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Noralf Trønnes <noralf@tronnes.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20210313112545.37527-3-noralf@tronnes.org

drivers/gpu/drm/drm_probe_helper.c

@@ -624,6 +624,7 @@ static void output_poll_execute(struct work_struct *work)
 	struct drm_connector_list_iter conn_iter;
 	enum drm_connector_status old_status;
 	bool repoll = false, changed;
+	u64 old_epoch_counter;
 
 	if (!dev->mode_config.poll_enabled)
 		return;
@@ -660,8 +661,9 @@ static void output_poll_execute(struct work_struct *work)
 
 		repoll = true;
 
+		old_epoch_counter = connector->epoch_counter;
 		connector->status = drm_helper_probe_detect(connector, NULL, false);
-		if (old_status != connector->status) {
+		if (old_epoch_counter != connector->epoch_counter) {
 			const char *old, *new;
 
 			/*
@@ -690,6 +692,9 @@ static void output_poll_execute(struct work_struct *work)
 				      connector->base.id,
 				      connector->name,
 				      old, new);
+			DRM_DEBUG_KMS("[CONNECTOR:%d:%s] epoch counter %llu -> %llu\n",
+				      connector->base.id, connector->name,
+				      old_epoch_counter, connector->epoch_counter);
 
 			changed = true;
 		}